Electronic control devices of this class have been known especially in plumbing units. They have visibly been increasingly used, on the one hand, in public facilities for hygienic reasons, and, on the other hand, generally to reduce the water consumption.
Such control devices for the contactless control of washing units have been known as well. These are based on an infrared sensor system. These have an infrared transmitter operating with continuous, pulsed radiated power. This transmitter is set such that the wash basin is not detected by an infrared receiver operating with an adjustable sensitivity, but an object, e.g., a hand, which is located in the intermediate zone, is. Thus, a contactless control device, which has an infrared light scanner installed in a water circuit, has become known from CH-A-646 766. When a hand is introduced into the detection zone of the light scanner, the latter responds. The detection zone is the area of intersection between a transmitted beam and a received beam. The transmitted power of the infrared radiation source is constant. To mask an existing background, the range of the system is correspondingly limited.
Furthermore, CH-A-651 143 discloses a contactless electronic control device, in which two signal transmitters arranged at spaced locations from one another are provided, which are alternatingly activated. In addition, two receivers are arranged near the signal transmitter, and they are connected such that a valve arranged in the water pipe is opened only when reflections of the signals of both signal transmitters are received. Since two transmitters and two receivers are both necessary, this control device is relatively expensive, and the energy consumption is relatively high.
Finally, a control device equipped with a radar probe has been known for controlling the flushing of a urinal. This probe is a direction recognizing probe and responds to an approaching movement as well as to a subsequent departing movement. This device is also relatively expensive.